In this proposal, a group of six faculty members in the Division of Chemistry and Chemical Engineering at the California Institute of Technology are requesting a shared 400 MHz nuclear magnetic resonance spectrometer. All are synthetic organic chemists;all but one (a recently hired assistant professor) have NIH funding. Three of the investigators (Grubbs, Reisman, Stoltz) have a strong focus on methodology;the others (Dervan, Dougherty, Hsieh-Wilson) have a more bio-organic focus. The requested instrument is intended to be a faster, more capable, and modern replacement for an antiquated 300 MHz instrument used for immediate characterization of newly synthesized compounds. It would be placed in a core facility where more than 50,000 spectra are acquired annually, but four of the seven instruments are 300 MHz spectrometers poorly matched to the needs of modern research at Caltech, and two of the three higher field instruments are quite old. The requested instrument would be a key component of a revitalized core facility at Caltech.